Answer:
Base price: $13.
Surcharge: $2 per additional pound.
Step-by-step explanation:
The base price can be considered a constant, while the surcharge is a function of the additional weight of the package, over 1 pound.
Then, we can model this as a linear function, with additional weight as the independent variable.
being b: base price, and s: surcharge for each additional pound.
The 7-pound package cost $25. The additional weigth in this case is 7-1=6 pounds.
The 22-pound package cost $55. The additional weigth is 21 pounds.
So we have the first point (6, 25):
Then, for the second point (21, 55) we have:
Then, the prices are:
Base price: $13.
Surcharge: $2 per additional pound.